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    <title>glProvokingVertex - OpenGL 4 Reference Pages</title>
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    <div class="refentry" id="glProvokingVertex">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>glProvokingVertex — specifiy the vertex to be used as the source of data for flat shaded varyings</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>C Specification</h2>
        <div class="funcsynopsis">
          <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
            <tr>
              <td>
                <code class="funcdef">void <strong class="fsfunc">glProvokingVertex</strong>(</code>
              </td>
              <td>GLenum <var class="pdparam">provokeMode</var><code>)</code>;</td>
            </tr>
          </table>
          <div class="funcprototype-spacer"> </div>
        </div>
      </div>
      <div class="refsect1" id="parameters">
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                <em class="parameter">
                  <code>provokeMode</code>
                </em>
              </span>
            </dt>
            <dd>
              <p>
                    Specifies the vertex to be used as the source of data for flat shaded varyings.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            <span class="emphasis"><em>Flatshading</em></span> a vertex shader varying output means to assign all vetices of the primitive the same value
            for that output. The vertex from which these values is derived is known as the <span class="emphasis"><em>provoking vertex</em></span> and
            <code class="function">glProvokingVertex</code> specifies which vertex is to be used as the source of data for flat shaded varyings.
        </p>
        <p>
            <em class="parameter"><code>provokeMode</code></em> must be either <code class="constant">GL_FIRST_VERTEX_CONVENTION</code> or
            <code class="constant">GL_LAST_VERTEX_CONVENTION</code>, and controls the selection of the vertex whose values are assigned to flatshaded
            varying outputs. The interpretation of these values for the supported primitive types is:
            </p>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: left; "/>
              <col style="text-align: left; "/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="bold"><strong> Primitive Type of Polygon <span class="emphasis"><em>i</em></span> </strong></span>
                            </th>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; "><span class="bold"><strong> First Vertex Convention </strong></span>
                            </th>
                <th style="text-align: left; border-bottom: 2px solid ; ">
                                <span class="bold"><strong> Last Vertex Convention </strong></span>
                            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                point
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span>
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span>
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                independent line
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                2<span class="emphasis"><em>i</em></span> - 1
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                2<span class="emphasis"><em>i</em></span>
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                line loop
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span>
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                <p>
                                <span class="emphasis"><em>i</em></span> + 1, if <span class="emphasis"><em>i</em></span> &lt; <span class="emphasis"><em>n</em></span>
                                </p>
                                <p>
                                1, if <span class="emphasis"><em>i</em></span> = <span class="emphasis"><em>n</em></span>
                                </p>
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                line strip
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span>
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span> + 1
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                independent triangle
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                3<span class="emphasis"><em>i</em></span> - 2
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                3<span class="emphasis"><em>i</em></span>
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                triangle strip
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span>
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span> + 2
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                triangle fan
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span> + 1
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span> + 2
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                line adjacency
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                4<span class="emphasis"><em>i</em></span> - 2
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                4<span class="emphasis"><em>i</em></span> - 1
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                line strip adjacency
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span> + 1
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                <span class="emphasis"><em>i</em></span> + 2
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                triangle adjacency
                            </td>
                <td style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                                6<span class="emphasis"><em>i</em></span> - 5
                            </td>
                <td style="text-align: left; border-bottom: 2px solid ; ">
                                6<span class="emphasis"><em>i</em></span> - 1
                            </td>
              </tr>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">
                                triangle strip adjacency
                            </td>
                <td style="text-align: left; border-right: 2px solid ; ">
                                2<span class="emphasis"><em>i</em></span> - 1
                            </td>
                <td style="text-align: left; ">
                                2<span class="emphasis"><em>i</em></span> + 3
                            </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
        </p>
        <p>
            If a vertex or geometry shader is active, user-defined varying outputs may be flatshaded by using the
            <code class="code">flat</code> qualifier when declaring the output.
        </p>
      </div>
      <div class="refsect1" id="notes">
        <h2>Notes</h2>
        <p>
            <code class="function">glProvokingVertex</code> is available only if the GL version is 3.2 or greater.
        </p>
      </div>
      <div class="refsect1" id="errors">
        <h2>Errors</h2>
        <p>
            <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>provokeMode</code></em> is not an accepted value.
        </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>Version Support</h2>
        <div class="informaltable">
          <table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
            <colgroup>
              <col style="text-align: left; "/>
              <col style="text-align: center; " class="firstvers"/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; "/>
              <col style="text-align: center; " class="lastvers"/>
            </colgroup>
            <thead>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
                <span class="bold"><strong>OpenGL Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Function / Feature Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>2.1</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.1</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.2</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.3</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.0</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.1</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.2</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.3</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.4</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>4.5</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">
                  <code class="function">glProvokingVertex</code>
                </td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">-</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2010-2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
      </div>
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